This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2001-284065 filed in Japan on Sep. 18, 2001, the entirety of which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a water jet propulsion apparatus, and more particularly to a water jet propulsion apparatus for use in a saddle type watercraft.
2. Description of the Background Art
As shown in FIG. 6, a water jet propulsion apparatus for a small boat is known int the background art, e.g., Japanese Utility Model Registration No. 2,548,210, the entirety of which is hereby incorporated by reference. The water jet propulsion apparatus is attached to a rear part of a boat and has a stator (duct) 1 forming a channel, an impeller 2 rotatably disposed within the stator 1, and an impeller shaft 3 rotatably supported by a bearing 1a in the stator 1 and coupled to the rear part of the impeller 2. A collar 4 is provided around the impeller shaft 3, and a waterproof seal 5 is provided between the collar 4 and the bearing 1a of the stator 1. A drive shaft 6 is coupled to the front part of the impeller 2.
When the drive shaft 6 is driven by an engine (not shown), the impeller 2 is rotated and a water stream is jetted rearward (to the right in the drawing), thereby propelling the boat body. In the above-described conventional water jet propulsion apparatus, since the front end 4a of the collar 4 is only in contact with the rear end 2a of the impeller 2, there is a problem in that water enters from a gap between the front end 4a of the collar 4 and the rear end 2a of the impeller 2. The water comes into contact with the surface of the impeller shaft 3, and corrodes the surface of the impeller shaft 3. This problem can be solved by making the impeller shaft 3 of a corrosion-resistant material,e g., such as stainless steel. However, the impeller shaft becomes undesirably expensive when corrosion resistant materials such as stainless steel are used in the design.
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
An object of the present invention is to provide a water jet propulsion apparatus that can solve the above problems and prevent water from coming into contact with the impeller shaft.
One or more of these and other objects are accomplished by a water jet propulsion apparatus comprising a stator forming a channel; an impeller rotatably disposed within the stator; an impeller shaft rotatably supported in the stator and coupled to the impeller; a collar provided around the impeller shaft; and a waterproof seal provided between the collar and the stator, wherein the collar is coupled to the impeller via the waterproof seal.
One or more of these and other objects are further accomplished by a water jet propulsion apparatus comprising a stator forming a channel; an impeller rotatably disposed within the stator; an impeller shaft rotatably supported in the stator and coupled to the impeller, wherein the impeller shaft is screwed to a rear part of the impeller; a collar provided around the impeller shaft; a waterproof seal provided between the collar and the stator, wherein the collar is coupled to the impeller via the waterproof seal; a drive shaft being spline-connected to the front part of the impeller; and a rubber buffer for a rear end of the drive shaft being provided within the propeller between a front end of the impeller shaft and the rear end of the drive shaft, the buffer including an engagement portion for engaging a screw hole in the boss of the impeller and a large diameter portion being attached to an internal face of the boss of the impeller.
In the aforementioned water jet propulsion apparatus, the collar is coupled to the impeller via the waterproof seal. Consequently, in the water jet propulsion apparatus, water does not enter from the gap between the collar and the impeller toward the impeller shaft. Therefore, corrosion on the surface of the impeller shaft is reduced or eliminated. As a result, it is not always necessary to make the impeller shaft of a corrosion-resistant material. Since a buffer for the rear end of the drive shaft is provided in the impeller between the front end of the impeller shaft in the impeller and the rear end of the drive shaft, shock at the time of attaching the impeller to the rear end of the drive shaft is lessened.
Without the present invention, at the time of screwing the impeller shaft to the rear part of the impeller, air (or grease) existing between the impeller shaft and the buffer cannot escape. Accordingly, the buffer may be excessively deformed. In contrast, the peripheral portion of the buffer is formed in a shape such that air escapes from the impeller shaft side toward the drive shaft side when the impeller shaft is screwed. Thus, excessive deformation of the buffer can be prevented.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.